Support arm for a crib mobile



FIG. 1 is a perspective view of a support arm for a crib mobile showing the new ornamental design;

FIG. 2 is a side view from one side, which is identical to a side view from the other side;

FIG. 3 is a front view of the support arm;

FIG. 4 is a rear view of the support arm;

FIG. 5 is a top view of the support arm; and,

FIG. 6 is a bottom view of the support arm. 

The ornamental design for a support arm for a crib mobile, as shown and described. 